ESIE10-01 Functional Control
Part 2 – Functional Description 2–45
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Capacity overrides -
limits of operation
The following conditions shall override automatic capacity control when the chiller is in COOL mode.
These overrides keep the circuit from entering a condition in which it is not designed to run.
■ Low Evaporator Pressure
If the Low Evaporator Pressure Hold event is triggered, the compressor will not be allowed to
increase in capacity.
If the Low Evaporator Pressure Unload event is triggered, the compressor will begin reducing
capacity.
The compressor will not be allowed to increase in capacity until the Low Evaporator Pressure
Hold event has cleared.
■ High Condenser Pressure
If the High Condenser Pressure Hold event is triggered, the compressor will not be allowed to
increase capacity. High Cond Hold Value = Max Saturated Condenser Value - 2.78°C
If the High Condenser Pressure Unload event is triggered, the compressor will begin reducing
capacity. High Cond Unload Value = Max Saturated Condenser Value - 1.67°C
The maximum saturated condenser temperature calculation is modelled after the compressor
operational envelope.
If Sat Evap Temp < 0°C then Max Sat Cond Temp = 1.596 (Sat Evap Temp) + 68.3°C
Otherwise, Max Sat Cond Temp = 68.3°C
The compressor will not be allowed to increase in capacity until the High Condenser Pressure
Hold event has cleared.
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